Which anomaly in unnormalized database allows insertion of duplicate partial information without main entity?

The correct answer is B: Insertion anomaly. Insertion anomaly occurs when you cannot insert data without complete information. Update anomaly = data inconsistency on updates. Deletion anomaly = loss of data when deleting.

For a sales database, to get top 5 products by revenue in each region, which window function approach is suitable?

The correct answer is A: ROW_NUMBER() OVER (PARTITION BY region ORDER BY revenue DESC). ROW_NUMBER() assigns unique numbers within each region partition, enabling row filtering. RANK() and DENSE_RANK() handle ties differently.

What is the difference between WHERE and HAVING clauses?

The correct answer is A: WHERE filters rows before grouping; HAVING filters groups after grouping. WHERE filters individual rows before GROUP BY is applied, while HAVING filters the grouped results after GROUP BY is applied.

Which type of JOIN returns only matching rows from both tables?

The correct answer is C: INNER JOIN. INNER JOIN returns only the rows that have matching values in both tables being joined.

Which SQL clause is used to sort the result set in ascending or descending order?

The correct answer is B: ORDER BY. The ORDER BY clause sorts the result set in ascending (ASC) or descending (DESC) order. Default is ascending.

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SQL Basics

SQL queries, DBMS, normalization, transactions

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All SQL Basics 57

Q.11 Easy SQL Basics

Which data type in SQL is used to store large text documents or binary data?

A VARCHAR

B TEXT

C BLOB

D CLOB

Correct Answer: C. BLOB

EXPLANATION

BLOB (Binary Large Object) stores large binary data. CLOB stores large text. TEXT is limited compared to BLOB/CLOB.

Test

Q.12 Easy SQL Basics

In SQL, which clause is used to filter groups based on aggregate function results?

A HAVING

B WHERE

C GROUP BY

D FILTER

Correct Answer: A. HAVING

EXPLANATION

HAVING clause filters groups created by GROUP BY, while WHERE filters individual rows before grouping.

Test

Q.13 Easy SQL Basics

Which statement is used to modify existing data in a table?

A MODIFY

B CHANGE

C UPDATE

D ALTER

Correct Answer: C. UPDATE

EXPLANATION

The UPDATE statement is used to modify existing records in a table.

Test

Q.14 Easy SQL Basics

What will be the output of: SELECT COUNT(*) FROM employees;

A The number of columns in the employees table

B The total number of rows in the employees table

C The names of all employees

D An error message

Correct Answer: B. The total number of rows in the employees table

EXPLANATION

COUNT(*) returns the total number of rows in the specified table, including NULL values.

Test

Q.15 Easy SQL Basics

Which SQL aggregate function returns the total sum of a numeric column?

A TOTAL()

B ADD()

C SUM()

D COUNT()

Correct Answer: C. SUM()

EXPLANATION

The SUM() function calculates the total sum of all values in a numeric column.

Test

Q.16 Easy SQL Basics

What is the correct syntax for inserting data into a table?

A INSERT INTO table_name VALUES (value1, value2, value3);

B INSERT table_name (value1, value2, value3);

C ADD INTO table_name VALUES (value1, value2, value3);

D INSERT VALUES table_name (value1, value2, value3);

Correct Answer: A. INSERT INTO table_name VALUES (value1, value2, value3);

EXPLANATION

INSERT INTO is the correct SQL syntax for inserting new records into a table, followed by the table name and VALUES clause.

Test

Q.17 Easy SQL Basics

Which keyword is used to eliminate duplicate rows in SQL results?

A UNIQUE

B DISTINCT

C DIFFERENT

D EXCLUDE

Correct Answer: B. DISTINCT

EXPLANATION

The DISTINCT keyword removes duplicate rows from the result set of a query.

Test

Q.18 Easy SQL Basics

What does the WHERE clause do in SQL?

A Sorts the results

B Filters rows based on specified conditions

C Groups the data

D Joins multiple tables

Correct Answer: B. Filters rows based on specified conditions

EXPLANATION

The WHERE clause is used to filter records that meet specified conditions in a SQL query.

Test

Q.19 Easy SQL Basics

Which SQL command is used to retrieve data from a database?

A SELECT

B RETRIEVE

C GET

D FETCH

Correct Answer: A. SELECT

EXPLANATION

SELECT is the standard SQL command used to retrieve or query data from one or more tables in a database.

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